1. Field of the Invention
The present invention relates to a vacuum breaker or air gap apparatus for use in liquid dispensing equipment, and particularly for use in water purification and dispensing systems such as reverse osmosis (RO) units.
2. Description of the Prior Art
In a reverse osmosis water dispenser, the source or inlet water passes through a membrane or the like and emerges as purified or potable outlet water. The water that is retained is waste or reject water which more or less constantly flows into the associated drainage system. This arrangement presents a risk that a drainage backflow can develop and contaminate the RO system.
Regardless of the particular type of water dispenser used, whether reverse osmosis or otherwise, if there is drainage into a sewer system, plumbing codes require use of an approved backflow prevention device, such as a vacuum breaker or air gap, to prevent backsiphoning or backflow of contaminated water into the dispensing system.
Contaminated water is considered to be any water located downstream of the potable water source, and an acceptable air gap apparatus therefore must be capable of preventing entry of such downstream water into the potable water system under any conceivable condition of operation.
In an air gap backflow prevention device, plumbing codes typically specify an air gap or vertical height opening of at least one inch. This is effective to prevent backsiphoning back flow in most situations, but there are instances when a pressure differential can develop so quickly that a high velocity flow of contaminated water bridges the air gap and passes into the potable water system.
Use of check valves would be one means for preventing such bridging backflow, but used alone they are not fail safe and are normally not allowed by most plumbing codes. This is because foreign matter in the backflow can clog such a valve and prevent it from seating properly.
Blockage of drain lines and resultant backflow has recently become more common because of the increasing use of water conservation devices such as low water consumption toilets and restricted flow rate shower heads. These reduce the rate of water flow and increase the susceptibility of drain lines to blockage and backflow. Then even a relatively slow rate of backflow in larger size drain lines becomes a high velocity backflow in the smaller size conduits of the potable water system.
Some manufacturers of RO systems fit their equipment with air gap devices, but most do not. Those that are provided do not always comply with plumbing codes, particularly the vertical air gap requirement. Further, such devices as are originally installed or which are later added by the RO unit installer do not provide both satisfactory downstream flow rates and protection against a forcible, high velocity upstream backflow.
Many prior art devices are aesthetically unappealing and relatively incessible, typically being cramped into a small space with the dispensing faucet.
What is needed is an inexpensive, relatively compact, non-integral or separate air gap device in kit form, adapted for mounting in an external location for accessibility, providing adequate flow rates and preferably including associated check valves for protection against pressurized backflows, and an associated trap to prevent entry of drainage system odors into the household. Such a kit would make installation within an RO system relatively easy, either as original equipment or as an after-fitted item. The trap portion of such a kit would also be useful in ordinary water cooler applications where it is desired to direct to a drain line the small quantity of water which collects in the drain cup, but where a connection to the building drain line upstream of the existing trap would be inconvenient or unsightly, or where the location of the existing trap is not known. With the present trap, a simple connection could be made to the building drain line at whatever point it was convenient.
My U.S. Pat. No. 4,646,775, issued Mar. 3, 1987, discloses an air gap apparatus capable of preventing back flow from a drain line, but the device employs a form of check valve which, as indicated above, is not permitted by most plumbing codes, and the device is not optimally configured for RO unit applications.
My U.S. Pat. Nos. 4,771,485 and 4,856,121, issued Sep. 20, 1988 and Aug. 15, 1989, respectively, also disclose forms of air gap apparatus, but the disclosed devices are designed for incorporation in a faucet fixture, and do not include any unique or special structure to prevent high velocity backflow of contaminated water into the fixture, other than a one inch air gap.